共查询到18条相似文献,搜索用时 156 毫秒
1.
热辐射与物质相互作用及辐射光子在物质中的传输是惯性约束聚变研究中的重要课题. 介绍了基于隐式蒙特卡罗方法的辐射输运方程,在该方程的积分-微分形式基础上,推导了利于蒙特卡罗方法模拟的等价的积分输运方程;基于积分方程设计数值模拟流程,编写三维蒙特卡罗数值模拟程序;针对热辐射输运典型问题及benchmark问题开展了数值实验,计算结果验证了方法的适应性及程序的正确性.
关键词:
热辐射
惯性约束聚变
输运方程
隐式蒙特卡罗 相似文献
2.
针对隐式蒙特卡罗方法模拟高温热辐射输运问题时存在的“辐射强度计算误差时间空间分布严重不均匀”现象,通过理论分析和数值模拟手段,找到决定误差大小的主要因素为“网格内的辐射径迹长度记录数”.据此提出“隐式蒙特卡罗全局降方差方法”并推导相应的计算公式.该方法主要包含如下3个关键技术:1)针对辐射输运蒙特卡罗模拟的自适应动态分配源粒子方法; 2)与自适应动态分配源粒子相匹配的动态权窗设计技术及粒子权无偏估计算法; 3)辐射强度的解析估计降方差方法.针对这3个关键技术,设计蒙特卡罗数值模拟方案,编写相应的数值模拟程序模块.典型辐射输运问题模拟结果显示:隐式蒙特卡罗全局降方差方法能够使网格辐射强度计算误差在整个时空范围内分布相对比较均匀,最大误差可控,计算效率提升10倍左右.新方法在激光惯性约束聚变的黑腔辐射输运模拟应用中取得了显著效果. 相似文献
3.
2015年在神光Ⅲ激光装置上开展了两孔球腔物理实验.利用三维隐式蒙特卡罗数值模拟程序模拟两孔球腔中的辐射输运问题,研究辐射场分布及其动态演化过程.数值模拟结果大多数与实验结果符合较好,但局部位置存在明显差异.分析了产生差异的可能原因,提出解决措施及未来发展方向.综合数值模拟结果及其与实验结果的对比可知,三维隐式蒙特卡罗数值模拟程序具备较好的黑腔三维辐射输运数值模拟能力. 相似文献
4.
利用隐式蒙特卡罗方法模拟热辐射光子在物质中的输运过程时,物质辐射源粒子是需要细致处理的物理量.传统的物质辐射源粒子抽样方法是体平均抽样方法,对于大多数问题,这样处理不会带来大的偏差.但是对于一些辐射吸收截面大、单一网格内温差显著的问题,体平均抽样方法的计算结果偏差较大.分析了产生偏差原因,提出一种基于辐射能量密度分布的辐射源粒子空间位置抽样方法,并推导了相应的抽样公式以解决此类问题.数值实验表明,新方法计算结果明显优于原方法且与解析结果基本一致. 相似文献
5.
6.
7.
求解介质内热辐射传递的双向统计蒙特卡罗法 总被引:2,自引:0,他引:2
基于热辐射传输的光路可逆性原理,提出了求解介质内热辐射传递的双向统计蒙特卡罗法(BSMC法)。该方法采用等温等权抽样,利用能束传输路径的可逆关系进行辐射传递的双向统计计算,充分利用了能束跟踪的计算信息。以二维矩形区域内吸收性介质的热辐射传递为例,介绍了BSMC的求解过程,分析了其计算误差。通过数值模拟,从辐射传递因子计算结果的倒易性满足程度与辐射平衡温度场两方面,将BSMC法与传统的蒙特卡罗法(TMC法)进行了比较。结果表明,在相同的计算量下,BSMC法比TMC有更高的模拟精度。 相似文献
8.
9.
10.
对于分子结构的优化和预测,蒙特卡罗(MC)是很重要的计算工具. 当溶剂效应被显式的考虑时,由于水分子和电离子的自由度很大,蒙特卡罗方法变得非常昂贵. 相对而言,基于隐式溶剂的蒙特卡罗方法可以通过对溶剂效应平均场的近似来大大降低计算成本,同时还能保持目标分子在原子水平上的细节. 目前两种最流行的隐式溶剂模型是泊松-波兹曼模型和通用化波恩模型. 通用化波恩模型是泊松-波兹曼模型的近似,但在模拟计算时间上要快得多. 本文通过结合两种隐式溶剂模型在准确性和效率方面的优势,开发了一种基于机器学习的隐式溶剂蒙特卡罗方法. 具体而言,蒙特卡罗方法通过机器学习既保留了泊松-波兹曼模型的精度,又达到了通用化波恩模型的速度,从而能快速准确地获取模拟计算中每一步的静电溶解自由能. 本文采用苯-水系统和蛋白质-水系统来验证我们的蒙特卡罗方法. 实验证明蒙特卡罗方法在分子结构优化和预测的速度和准确性方面具有很大优势. 相似文献
11.
星载多波段红外光学系统的杂散辐射分析 总被引:2,自引:0,他引:2
引入反向蒙特卡罗法与双向蒙特卡罗法对红外光学系统的杂散辐射进行分析,基于光谱辐射传递因子导出了焦平面辐射能流计算式.以某星载多波段红外光学系统为例,在检验计算可靠性的基础上,模拟了各波段辐射能从地球背景和光机内壁面到焦平面的传播过程,分析了壁面吸收率与温度的影响.结果表明,采用双向蒙特卡罗法可有效地模拟辐射能从地球向星载光学系统焦平面的传播过程,采用反向蒙特卡罗法可容易地分析光机内部热辐射的影响;光机内壁面吸收率对视场外杂散辐射的传播有很大影响,温度高于250 K的光机内壁面热辐射成为主要的杂散光源. 相似文献
12.
13.
L.H. Liu H.C. Zhang H.P. Tan 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(3):357-362
A Monte Carlo discrete curved ray-tracing method is developed to analyze the radiative transfer in one-dimensional absorbing-emitting semitransparent slab with variable spatial refractive index, in which the Monte Carlo method is combined with the discrete curved ray-tracing method. A problem of radiative equilibrium with linear variable spatial refractive index is taken as an example to examine the accuracy of the proposed method. The temperature distributions and the dimensionless radiative heat flux are determined by the proposed method and compared with the data in references, which are obtained by other different methods. The results show that the Monte Carlo discrete curved ray-tracing method has a good accuracy in solving the radiative transfer in one-dimensional semitransparent slab with variable spatial refractive index. 相似文献
14.
15.
L.A. Dombrovsky W. Lipiński 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,103(3):601-610
An approximate numerical method for fast calculations of the radiation heat transfer in a solar thermochemical reactor cavity is formulated based on the separate treatment of the solar and thermal radiative exchange by the diffusion approach. The usual P1 approximation is generalized by applying an equivalent radiation diffusion coefficient for the optically thin central part of the cavity. The resulting boundary-value problems are solved using the finite element algorithm. The accuracy of the model is assessed by comparing the results to those obtained by a pathlength-based Monte Carlo simulation. The applicability of the proposed model is demonstrated by performing calculations for an example problem, which incorporates a range of parameters typical for a solar chemical reactor and the spectral radiative properties of polydisperse zinc oxide particles. 相似文献
16.
Jeffery D. Densmore Kelly G. Thompson Todd J. Urbatsch 《Journal of computational physics》2012,231(20):6924-6934
Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Implicit Monte Carlo radiative-transfer simulations in optically thick media. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many smaller Monte Carlo steps, thus improving the efficiency of the simulation. In this paper, we present an extension of DDMC for frequency-dependent radiative transfer. We base our new DDMC method on a frequency-integrated diffusion equation for frequencies below a specified threshold, as optical thickness is typically a decreasing function of frequency. Above this threshold we employ standard Monte Carlo, which results in a hybrid transport-diffusion scheme. With a set of frequency-dependent test problems, we confirm the accuracy and increased efficiency of our new DDMC method. 相似文献
17.
Yong Shuai 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(7):1281-1296
Using Monte Carlo method, the paper investigates the radiative heat transfer in participating media. Based on the radiative exchange factor, an uncertainty analysis of Monte Carlo method is undertaken and the corresponding mathematical expressions are deduced to predict its accuracy. Furthermore, randomness properties of pseudorandom number generators are investigated, and a model to test radiation symmetry is adopted to validate the performance of some generators. The paper studies the effects of energy bundle numbers, discretization schemes, emission location, optical thicknesses, wall emissivity and CPU time on the numerical accuracy. In addition, the simulation results are proved to give a reference for using Monte Carlo method, which is applicable for calculation of the radiative exchange factor. 相似文献
18.
A Monte Carlo method for 3D thermal infrared radiative transfer 总被引:1,自引:0,他引:1
Y. Chen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,101(1):166-178
A 3D Monte Carlo model for specific application to the broadband thermal radiative transfer has been developed in which the emissivities for gases and cloud particles are parameterized by using a single cubic element as the building block in 3D space. For spectral integration in the thermal infrared, the correlated k-distribution method has been used for the sorting of gaseous absorption lines in multiple-scattering atmospheres involving 3D clouds. To check the Monte-Carlo simulation, we compare a variety of 1D broadband atmospheric fluxes and heating rates to those computed from the conventional plane-parallel (PP) model and demonstrate excellent agreement between the two. Comparisons of the Monte Carlo results for broadband thermal cooling rates in 3D clouds to those computed from the delta-diffusion approximation for 3D radiative transfer and the independent pixel-by-pixel approximation are subsequently carried out to understand the relative merits of these approaches. 相似文献